Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the annotations (readOnlyHint=false, destructiveHint=false, idempotent=false), the description discloses genuinely useful behavior: passwords are write-only and never returned, verification calls are rate limited per number and per workspace, outbound is refused until ownership is confirmed, and test calls are billed under calls:write. What it fails to disclose is the side effect of this specific tool — whether arming changes future inbound routing or is reversible. No annotation contradiction, since it never claims a read-only operation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The single dense paragraph front-loads generic SIP CRUD context rather than the tool's own action, and spends most of its length documenting the behavior of three sibling tools. The operative information about what arm_sip_connection_inbound_test itself does is absent, so the word count is working against clarity rather than for it.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

This is a non-idempotent, non-destructive mutation with probable side effects, three undocumented parameters, and no output schema. The description supplies useful ecosystem and cost/rate context but leaves the agent without the two things it most needs: what is mutated and what is returned.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description carries the full burden for connection_id, number_id, and project_id. It adds only loose narrative references to 'a carrier SIP connection and its numbers' and 'that number' without establishing which identifier is which, the format, or the role of project_id. This does not compensate for the coverage gap.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The name and required parameters (connection_id, number_id) suggest arming an inbound test for a specific number, but the description never states that action. Instead it describes the broader SIP-connection CRUD surface ('create, read or change a carrier SIP connection'), which belongs to sibling tools like create_sip_connection and update_sip_connection. An agent cannot confidently tell what this specific invocation does.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It does route an agent toward related tools (check_sip_connection_number_ownership, start_sip_connection_test_call, check_sip_connection_reachability) and notes that attaching a number triggers verification. However, it never says when to choose this tool over attach_sip_connection_number, update_sip_connection, or disable_sip_connection, nor what preconditions apply before arming.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.